Create a surface within bounding curves?
Add a Curve (Shift+A-->Curve-->Bezier) and model the first profile being in Edit Mode. When finished, select it (A), duplicate (Shift+D) and place as far from the first one as you want. Model the duplicated second profile as you like.


Go to Object Mode, change the curve's resolution (Preview U and Render U) to 3, then select it and press Alt+C-->Convert to Mesh.


Go to User Preferences (Ctrl+Alt+U) and enable the F2 add-on.


Select two vertices as pictured below and press F continuously to fill the gaps.


Add a Subsurf Modifier to the mesh to make it look smoother. Enable a Smooth Shading in the Edit panel of a Tool Shelf (T).